Reciprocating pumps draw and discharge a liquid by reciprocating a moving component such as a plunger, a piston, or a diaphragm in a pump housing such as a cylinder or a chamber. In a plunger pump 60, as shown in FIG. 6, a cylinder 62 is provided in a pump head 61, and a seal 65 is used for liquid-tight insertion of a plunger 66 into an end of the cylinder 62. The plunger 66 is reciprocally moved in the cylinder 62 with a predetermined cam profile by a motor M and a cam 67 so as to draw a liquid through a drawing port 63 and discharge it through the discharge port 64 (Patent Document 1).
Reciprocating pumps can be stably operated for a long time as they have relatively simple structure. Therefore, a reciprocating pump is often used for a delivery of a liquid for a long time in a liquid chromatograph or other devices. Reciprocating pumps include, other than a plunger pump as mentioned above, a piston pump, a diaphragm pump (membrane pump), and other pumps.